Non-human animals, e.g., mice, have been genetically engineered to be useful tools in methods for making antibody sequences for use in antibody-based human therapeutics. Mice with humanized variable region loci (e.g., VH, DH, and JH genes, and VL and JL genes) are used to generate cognate heavy and light chain variable domains for use in antibody therapeutics. Other mice are available that generate fully human antibodies with cognate heavy and light chains.
Human antibody therapeutics are engineered based on desired characteristics with respect to certain pre-selected antigens. Humanized mice are immunized with the pre-selected antigens, and the immunized mice are used to generate antibody populations from which to identify high-affinity cognate heavy and light variable domains with desired binding characteristics. Some humanized mice, such as those having a humanization of just variable regions at endogenous mouse loci, generate populations of B cells that are similar in character and number to wild-type mouse B cell populations. As a result, an extremely large and diverse population of B cells is available in these mice from which to screen antibodies, reflecting a large number of different immunoglobulin rearrangements, to identify heavy and light variable domains with the most desirable characteristics.
But not all antigens provoke an immune response that exhibits a very large number of rearrangements from a wide selection of variable (V) segments. That is, the human humoral immune response to certain antigens is apparently restricted. The restriction is reflected in clonal selection of B cells that express only certain V segments that bind that particular antigen with sufficiently high affinity and specificity. Some such antigens are clinically significant, i.e., a number are well-known human pathogens. A presumption arises that the V segment expressed in the human immune response is a V segment that, in combination with a human D and a human J segment, is more likely to generate a useful high affinity antibody than a randomly selected V segment that has not been observed in a human antibody response to that antigen.
It is hypothesized that natural selection, over millennia, has selected the most efficient foundation or base from which to design a most effective weapon for neutralizing human pathogens—a clonally selected V segment. There is a need in the art for more and superior antibodies that bind and/or neutralize antigens such as the pathogens discussed above. There is a need to more rapidly generate useful sequences from selected V segments, including polymorphic and/or somatically mutated selected V segments and to more rapidly generate useful populations of B cells having rearrangements of the V segments with various D and J segments, including somatically mutated versions thereof, and in particular rearrangements with unique and useful CDR3s. There is a need for biological systems, e.g., non-human animals (such as, e.g., mice, rats, rabbits, etc.) that can generate therapeutically useful antibody variable region sequences from pre-selected V segments in increased number and diversity than, e.g., can be achieved in existing modified animals. There is a need for biological systems engineered to have a committed humoral immune system for clonally selecting antibody variable sequences derived from restricted, pre-selected V segments, including but not limited to cognate human heavy and light chain variable domains, useful in the manufacture of human antibody-based therapeutics against selected antigens, including certain human pathogens.
There is a need in the art for therapeutic antibodies that are capable of neutralizing viral antigens, e.g., HIV and HCV, including antigen-specific antibodies containing heavy chains derived from a single human variable segment, and for a system that produces a diverse source of antibodies from which to select therapeutic antibody sequences. There is also a need for further methods and non-human animals for making useful antibodies, including antibodies that comprise a repertoire of heavy chains derived from a single human VH segment and having a diverse set of CDR sequences, and including such heavy chains that express with cognate human light chain variable domains. Methods are needed for selecting CDRs for immunoglobulin-based binding proteins that provide an enhanced diversity of binding proteins from which to choose, and enhanced diversity of immunoglobulin variable domains, including compositions and methods for generating somatically mutated and clonally selected immunoglobulin variable domains for use, e.g., in making human therapeutics.